Intercommunication telephone system.



PATENTED JANEEIS, 1903; T. SLOPEB. a; I. H. PARSONS.IANTERAGOMMUNIIOATION TELEPHONE SYSTEM.

APPLIOATIOKIILLBD APB. I8, 1902 80 MODEL.

THOMAS SLOPER, OF WILTS, AND ISAAC HARDY PARSONS, OF

ENGLAND.

LEICESTER,

INTERCOMM UNICATION TELEPHONE SYSTEM.

SPECIFICATION formingpart of Letters Patent N 0. 718,224, dated January13, 1903.

Application filed April 18' 1902.

To all whom it may concern.-

Be it known that we, THOMAS SLoPER, of'l i Brittox, Devizes, Wilts, andISAAC HARDY PARSONS, of Faraday Works, Leicester, England, subjects ofthe King of Great Britain, have invented new and useful Improvements inIntercommunication Telephone Systems, of which the following is aspecification.

This invention relates to improvements in intercommunication telephonesystems of the kind wherein each instrument is provided with a pair ofhome lines having extensions or forks whereby the said lines can be con;nected to jacks or connecting devices at other instruments of thesystem. In such systems as heretofore constructed it is possible for aperson to tap or overhear a conversation being carried on between twosubscribers by simply connecting his switch to one of thespeaking-lines, and it is even found in practice that overbearing cantake place if only one terminal of the receiver at the tappingstation isconnected to any part of a speaking-line.

Now this invention has for its object to obviate this defect, and tothis end instead of connecting both the transmitter and the receiver ofeach instrument to the same lines or the same induction coil, as hasheretofore 0 been the practice, we arrange the connections in such amanner that the receiver at each instrument is always disconnected fromthe transmitting apparatus of the same instrument and also from theswitch or other device made use of for connection with the lines of theother stations of the system, and from the earth or common return-wire,(if any.) By transmitting apparatus we mean the microphoneinduction-coil or other apparatus for producing the necessary current orvaria tion of potential either directly or by induction. With thisarrangement it will be understood that the operator at each instrumentcannot connect his receiver to any other line than his own, so thatalthough he can hear what is spoken into his own pair of lines from anyof the stations yet he can only speak to the station to the lines ofwhich he is connected by his plug or switch.

In the accompanying drawings, Figure 1 is a diagrammatic viewrepresenting two tele- Serial No. 103,652. (No model.)

phone-stations connected up according to the invention. Fig. 2 is asimilar view illustrating a slight modification.

The same characters of reference refer to the same or correspondingparts in both figures.

A and B represent the two stations.

at a are the receivers; b b, the receiverhooks; c c, the transmitters; dd, the bells; e e, the switches or plugswhich are adapted. to beconnected to the jacks ff for connecting up the two stations, ashereinafter described.

g is the battery in the transmitter-circuit, and 1, 2, 3, 4., 5, and 6represent the home lines with which receivers of the different stationsare connected, the jacks f f being also connected to these lines, asclearly shown. With this arrangement when an operator at, say, station Adesires to call up an operator at station E he brings his plug a inconnection with the jacks f f, attached to the lines 1 and 2, anddepresses the key or contact '9, whereupon the current flows through thewire 7, contact g, wire 8, plug 6, jack f, home line 2, wire 9 atstation E, bell d, receiver-hook b, wire 10, home line 1, jack f atstation A, plug e, and wire 11 back to the battery. The bell at stationE is therefore rung, announcing to the operator in this station thatsome one wishes to speak to him. 7 He must therefore remove his receiverfrom its hook, thereby placing it in circuit with the transmitter at thecalling-station A, the operator at which station can then announce tohim his number. Upon receiving the number the operator at station Bplaces his plug e into connection with the home lines corresponding tostation A, whereupon his transo mitter is brought into electricalconnection with the receiver at station A, thus enabling the operator atthe second station to converse. It will thus be seen that the receiverat each station is in connection only with the 5 transmitter at theother stationthat is 'to say, with the station to which it isconnectedby means of the plug or switch-so thatit is impossible for an operatorat a third station to overhear the conversation which is proceeding, ashis home line cannot be brought into electrical connection with thetransmitter at either of the stations between which conversation isproceedin 72. is a buzzer or other suitable sounding device which isused for indicating to the operator at the calling-station that his callis answered, and in the arrangement shown in Fig. 1 this buzzer isinserted in the signalingcircuit, beingadvantageously operated by thesignaling-current, although an independent signaling-current at thecalled station may be used, if found more convenient.

In order that the signaling-current at a third station shall not be sentthrough a receiver at either one of the two stations in conversation, wemay connect one terminal of the bell at each station to a commonreturn-line 11 or earth, as is indicated in the arrangement shown inFig.2. In this arrangement we have shown a magneto-machine 7' forgenerating the necessary current for signaling purposes, although wewish it to be understood that an ordinary ringing-battery could beemployed, if desired, and also that such a magneto-generator could beused for ringing in the arrangement shown in Fig. 1 in lieu of thebattery there illustrated.

When the connections are made as shown in Fig. 2 and the subscriber atstation A desires to ring up the subscriber at station B, the subscriberat the former station operates his magneto-generatorj so as to cause acurrent to flow from the said generator through the line 11, switch-plug9, jack f, home line 1, line 10 at station E, receiver-hook Z), bell d,and common return-line or earth 2' back to the generator A key may beprovided at 7a, which may be operated by hand while ringing, or it maybe so arranged that it is automatically operated when the generator isused.

Assume now that the receiver at station B is removed from its hook andthat a subscriber at another station endeavors to ring up station E. Inthis case the circuit between the home line 1 and the return-wire t' isbroken at the receiver-hook b, so that no current flows, and thus thesubscriber using the receiver-at station E is not subjected to theannoyance of being rung up while he is using the receiver. At the sametime the subscriber at the calling-station is made aware that thesubscriber at station E is engaged, as he receives no announcement onhis sounder that his signal has been received.

Having now particularly described and ascertained the nature of oursaidinvention and in what manner the same is to be performed, we declarethat what we claim is 1. In an intcrcommunication telephone system, thecombination of a plurality of stations each having a receiver, a circuitfor the receiver extending to the other stations, and a transmitter atall times entirely discon nected from the said receiver-circuit, andadapted to be connected to the receiver-circuit of another station,substantially as described.

2. In an intercommunication telephone system, the combination of aplurality of stations each provided with a transmitter and a receiver atall times in a different circuit from the transmitter, and means forconnecting the transmitter of one station with the receiver only ofother stations, substantially as described.

3. In an intercom munication telephone system, the combination of aplurality of stations each provided with a transmitter and a receiver ina diiferent circuit from the transmitter, a plurality of linesconnecting said stations, and a circuit-controlling device for eachstation, in the transmitter-circuit thereof for connecting saidtransmitter with the receiver of a called station, substantially asdescribed.

4. In an intercommunication telephone system, the combination of aplurality of stations, each station having its receiver and transmitterin separate and independent circuits and a circuit-controller in acircuit independent of the receiver circuit for connecting thetransmitter of one station to the receiver of other stations,substantially as described.

5. In an intercommunication telephone system, the combination of aplurality of stations, each having a receiver and a transmitter and apair of home-line wires connected to its receiver only, and extending toeach of the other stations and means at each station for placing thetransmitter only thereof in connection with the home lines leading tothe receiver only of another station, substantially as described.

6. In an intercommunication telephone system, the combination of aplurality of stations each having a receiver, a pair of home lines forthe receiver leading to each of the other stations, a call device in ashunt-circuit connected with said home lines, a transmitter, at alltimes disconnected from said home lines leading to the receiver, acircuit-controller for connecting said transmitter with the home lines,of another station, and a switch for cutting the said call device out ofthe receivercircuit and placing the receiver in said circuit,substantially as described.

7. In anintercommunication telephone system, the combination of aplurality of stations each having a receiver, a pair of home linestherefor, leading to all the other stations, a call device in a shunt ofthe receivercircuit, a switch for cutting out said call device andplacing said receiver in connection with said home lines, a transmitterat all times disconnected from said home lines, a separate circuit forsaid transmitter, a controller in said circuit for placing thetransmitter in connection with the home lines leading to the receiver ofanother circuit and an electric signal in said transmitter circuit,substantially as described.

8. In an intercommunication telephone system, the combination of aplurality of stations each having a receiver, a pair of home linestherefor, leading to all the other stations, a call device in a shunt ofthe receivercircuit, a switch for cutting out said call device andplacing said receiver in connection with said home lines, a transmitterat all times disconnected from said home lines, a separate circuit forsaid transmitter, a controller in said circuit for placing thetransmitterin connection with the home lines leading to the receiver ofanother circuit, an electric signal in a shunt-circuit in saidtransmitter-circuit and a switch for cutting said signal into and out ofsaid circuit, substantially as described.

9. In an intercommunication telephone system, the combination of aplurality of stations each provided with a receiver, a circuit thereforincluding a pair of home lines leading to all the other stations, a calldevice in a shunt-circuit of said receiver-circuit, a

THOMAS SLOPER. ISAAC HARDY PARSONS.

Witnesses:

O. G. REDFERN, A. ALBUTT.

